1. Technical Field
The present invention relates to a switch apparatus.
2. Related Art
Conventionally, a power semiconductor device that handles a large amount of power is known as a switch apparatus used for ignition in an internal combustion engine, for example. A circuit driving such a power semiconductor device is known that uses a timer circuit or the like to detect when an abnormal state such as excessive current, overheating, or the like occurs in the power semiconductor device and includes a circuit that protects the internal combustion engine from the effects of such abnormalities, such as shown in Patent Documents 1 and 2, for example.    Patent Document 1: Japanese Patent Application Publication No. 2002-4991    Patent Document 2: Japanese Patent Application Publication No. 2006-109286
The timer circuit that detects abnormalities in the power semiconductor device preferably uses a control signal supplied to a drive circuit of the power semiconductor device as an operating power source, and does not use a specialized power source. In other words, a drive circuit for a power semiconductor device is desired that operates stably and has a small circuit size, without including a power supply input, input circuit, or the like specialized for the timer circuit.